1. Field of the Invention
The present invention relates, in general, to stereoscopic image generation, and, more particularly, to systems and methods for producing stereoscopic images for three-dimensional (3D) projection or display, with at least a portion of the images being generated to provide unique or special effects such as at scene transitions.
2. Relevant Background
There is a growing trend toward using 3D projection techniques in theatres and in home entertainment systems including video games and computer-based displays. Using 3D projection techniques the right eye and the left eye images can be delivered separately to display the same scene or images from separate perspectives so that a viewer sees a three dimensional composite, e.g., certain characters or objects appear nearer than the screen and others appear farther away than the screen. Stereoscopy, stereoscopic imaging, and 3D imaging are labels for any technique capable of recording 3D visual information or creating the illusion of depth in an image. The illusion of depth in a photograph, movie, or other two-dimensional image is created by presenting a slightly different image to each eye. Traditional stereoscopic photography creates a 3D illusion starting from a pair of 2D images. In most live action and animated 3D projection systems, depth perception in the brain is achieved by providing to the eyes of the viewer two different images, representing two perspectives of the same object, with a minor deviation similar to the perspectives that both eyes naturally receive in binocular vision.
The images or image frames used to produce such a 3D output are often called stereoscopic images or a stereoscopic image stream because the 3D effect is due to stereoscopic perception by the viewer. A frame is a single image at a specific point in time, and motion or animation is achieved by showing many frames per second (fps) such as 24 to 30 fps. The frames may include images or content from a live action movie filmed with two cameras or a rendered animation that is imaged or filmed with two camera locations. Stereoscopic perception results from the presentation of two horizontally offset images or frames with one or more object slightly offset to the viewer's left and right eyes, e.g., a left eye image stream and a right eye image stream of the same object. The amount of offset between the elements of left and right eye images determines the depth at which the elements are perceived in the resulting stereo image. An object appears to protrude toward the observer and away from the neutral plane or screen when the position or coordinates of the left eye image are crossed with those of the right eye image (e.g., negative parallax). In contrast, an object appears to recede or be behind the screen when the position or coordinates of the left eye image and the right image are not crossed (e.g., a positive parallax results).
Many techniques have been devised and developed for projecting stereoscopic images to achieve a 3D effect. One technique is to provide left and right eye images for a single, offset two-dimensional image and displaying them alternately, e.g., using 3D switching or similar devices. A viewer is provided with liquid crystal shuttered spectacles to view the left and the right eye images. The shuttered spectacles are synchronized with the display signal to admit a corresponding image one eye at a time. More specifically, the shutter for the right eye is opened when the right eye image is displayed and the liquid crystal shutter for the left eye is opened when the left eye image is displayed. In this way, the observer's brain merges or fuses the left and right eye images to create the perception of depth.
Another technique for providing stereoscopic view is the use of anaglyph. An anaglyph is an image generally consisting of two distinctly colored, and preferably, complementary colored, images. The theory of anaglyph is the same as the technique described above in which the observer is provided separate left and right eye images, and the horizontal offset in the images provides the illusion of depth. The observer views the anaglyph consisting of two images of the same object in two different colors, such as red and blue-green, and shifted horizontally. The observer wearing anaglyph spectacles views the images through lenses of matching colors. In this manner, the observer sees, for example, only the blue-green tinted image with the blue-green lens, and only the red tinted image with the red lens, thus providing separate images to each eye. The advantages of this implementation are that the cost of anaglyph spectacles is lower than that of liquid crystal shuttered spectacles and there is no need for providing an external signal to synchronize the anaglyph spectacles. In other 3D projection systems, the viewer may be provided glasses with appropriate polarizing filters such that the alternating right-left eye images are seen with the appropriate eye based on the displayed stereoscopic images having appropriate polarization (two images are superimposed on a screen, such as a silver screen to preserve polarization, through orthogonal polarizing filters). Other devices have been produced in which the images are provided to the viewer concurrently with a right eye image stream provided to the right eye and a left eye image stream provided to the left eye. Still other devices produce an auto-stereoscopic display via stereoscopic conversion from an input color image and a disparity map, which typically has been created based on offset right and left eye images. While these display or projection systems may differ, each typically requires a stereographic image as input in which a left eye image and a slightly offset right eye image of a single scene from offset cameras or differing perspectives are provided to create a presentation with the appearance of depth.
With the recent growing surge in development and sale of 3D projection systems and devices, there is an increased demand for new and exciting content. For example, there is a demand for films, video games, and other 3D works that include imagery that provides high quality 3D effects but also provides other unique and surprising effects. As a result, there remains a need for improved ways to generate stereoscopic images for use with existing as well as future 3D projection systems.